Scientists demystify 'Wall Paper Peeling Mystery'

Published: Monday, May 12, 2008, 11:28 [IST]

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Washington, May 12 : Scientists have explained the physics behind the frustrating experience of removing adhesive paper from a surface and getting a pointy flap as a result, which is popularly known as the 'Wall Paper Peeling Mystery'.

According to a report in Science Daily, the mystery behind this phenomenon has been solved by a team from the Laboratoire de physique et mecanique des milieux heterogenes in France, collaborating with the University of Santiago in Chile and with MIT in the US.

With his Chilean and American colleagues, Benoit Roman, from the Laboratoire de physique et mecanique des milieux heterogenes, has studied the problem from a theoretical and experimental point of view.

The researchers have set up a system for controlled tear experiments: an adhesive film is glued to a surface, two slits are cut, and the system then provides a steady pull on the tab.

The researchers then record the shapes of the flaps and the mechanical forces involved, for films with different adhesive and mechanical properties.

When the tab is pulled, after the two slits are cut, the flap stores elastic energy. The system tends to dissipate this energy by minimizing the size of the fold.

The slits are naturally drawn to the areas of the system which are the most sollicited, namely those containing the greatest amount of elastic energy.

In this case, that would be the folded part of the tab. They are irrepressibly drawn to each other, gradually reducing the size of the tab.

By analyzing these observations, the physicists have shown that the shape of the flaps is a triangle, with an angle depending on three characteristics of the adhesive material: its adhesion, its flexibility, and its resistance to tearing.

The researchers have put together a formula which allows the characterization of one of these properties based on the other two and on a simple measurement of the angle of the triangle.

Materials engineers could use these results in industry to calculate one of the three properties when the other two are known.

This could be particularly useful for the characterization of ultra-thin films, which are difficult to manipulate and which are basic elements in micro- or nano-systems.